The present invention relates to a zinc oxide varistor which absorbs dielectric lightning surge, electrostatic surge, burst surge or the like, and a method of manufacturing same.
As a conventional zinc oxide varistor, the following zinc oxide varistor is generally known.
First, a material based on zinc oxide is sintered to make a varistor element. A first external electrode is formed on the surface of the sintered varistor element. Next, the varistor element is buried into a mixture based on SiO2 and is subjected to heat treatment. Thus, Zn2SiO4 film having acid and alkali resistance is formed on the surface of the varistor element. To have acid and alkali resistance means to have plating resistance. Then, Zn2SiO4 film is also formed on the first external electrode, resulting in generation of irregularities thereon. In order to eliminate such irregularities and to assure electrical connection with external circuits, a second external electrode is formed on the first external electrode. After that, Ni plating and solder plating are performed on the second external electrode.
However, in the conventional configuration as described above, it is necessary, after forming the first external electrode, to again perform heat treatment in SiO2, to remove deposits, and to form the secondary external electrode. Accordingly, there has been a problem that the manufacturing process becomes very complicated.
In order to solve such problem, the present invention is intended to provide a zinc oxide varistor having a Zn2SiO4 film on the surface of the varistor element, requiring no heat treatment in SiO2 after forming the first external electrode, that is, after sintering the varistor element.
A method of manufacturing a zinc oxide varistor of the present invention comprises:
(a) a first process of forming a varistor element whose main component is zinc oxide, and
(b) a second process of sintering the varistor element,
wherein by sintering the varistor element, the varistor element is sintered, and zinc compound having at least one of acid resistance and alkali resistance is precipitated and formed on the surface of the varistor element.
Preferably, the method of manufacturing the zinc oxide varistor further comprises:
(c) a process of attaching an external electrode to the varistor element, wherein the external electrode attaching process is performed after finishing the process of sintering the varistor element.
A zinc oxide varistor of the present invention comprises:
a varistor element whose main component is zinc oxide; and
a precipitate film formed on the surface of the varistor element;
wherein the precipitate film is more excellent in alkali resistance or acid resistance than the varistor element.
Preferably, the zinc oxide varistor further comprises an external electrode disposed on the surface of the varistor element.
By this configuration, a precipitate film having plating resistance may be formed on the surface of the varistor element during sintering process. As a result, it is possible to shorten the manufacturing process, and also, to improve the productivity. Plating resistance means that no deterioration occurs during plating process.